Tunable wideband SAW-less receiver front-end in 65 nm CMOS

A surface acoustic wave-less receiver front-end for GSM, TD-LTE and TD-SCDMA standards featuring a novel low noise amplifier (LNA) architecture and harmonic rejection technique is presented. The two-stage LNA uses capacitive feedback in the first stage for wideband input matching. It can operate from 500 MHz up to 2.5 GHz with an S₁₁ below ?15 dB. The harmonic rejection mixer structure operates using two- and four-phase local oscillator signals and is capable of achieving a high harmonic rejection over a wide channel bandwidth. The average harmonic rejection is above 60 dB measured over a 20 MHz LTE channel and above 70 dB over a GSM channel. The mixer structure contains digitally tunable resistor and capacitor banks for precise tuning, causing the peak harmonic rejection in the channel to exceed 80 dB. The precise tuning capability ensures good harmonic rejection in the presence of process mismatch and duty cycle mismatch. The 1-dB received signal compression point with a blocker present at 20/80 MHz offset for low-/high-band is 0 and +2 dBm, respectively. In-band IIP3, and IIP2 are ?14.8 and >49 dBm, respectively, for low-band. For high-band they are ?18.2 and >44 dBm. Implemented in 65 nm CMOS, the complete front-end consumes 80 mW of power.     

Radiation Q of a Small Antenna Enclosed in an Oblate Spheroidal Volume: Transverse-to-Axis Polarisation

Radiation quality factor, Q, of an electrically small lossless structure that fits an oblate spheroidal volume for transverse-to-axis polarisation is investigated. Q is evaluated for different size and shape of a spheroid by integrating numerically the stored energy associated with radiation. It is found that Q depends on the distribution of power amongst the various spheroidal modes, and a minimum of Q is achieved by suitable optimisation of the relative amplitudes of these modes. A graphical comparison between the minimum Q of a transversally polarised oblate and an axially polarised prolate spheroid is provided for ellipticities in the range 0.2,…,1. The inverse of the obtained minimum Q serves as an estimate for the bandwidth potential of an arbitrary, linearly polarised lossless radiator inside that volume.     

Perpendicular to grain stiffness of timber cross sections as affected by growth ring pattern, size and shape

A finite element plane stress parameter study of the global perpendicular to grain stiffness of timber structural elements such as beams and cross ties is presented. This stiffness is affected by the size and shape of the cross section, the growth ring pattern, the stiffness properties of the wood and the boundary conditions. Various rectangular sections with concentric circular growth rings with systematic variation of pith location were studied for elastic orthotropic wood properties corresponding to a softwood species and a hardwood species. Two conventional and two periodic boundary conditions were considered. The results are presented in diagrams. Growth ring pattern and cross section size were found to be of great importance for the stiffness, in particular for softwood elements. Global stiffness for material properties representing Norway spruce differed with a factor 7 between stiffest and weakest growth ring pattern. The influence of boundary conditions appears in comparison to be small.